The present invention relates to an optical reproducing system for optically reproducing signals such as voices or images recorded in concave and convex areas on a record medium, for example, a record disc.
Conventional systems for optically reproducing such a signal have commonly utilized three beams of diffracted light with the zero order and plus and minus first orders produced by the diffraction grating to reproduce the signal while producing a control signal that causes the three beams of diffracted light focussed on the record disc to follow the information track thereon. Conventional systems of the type referred to have inevitably employed a complicated optical system including a diffraction grating and associated optical components and have made it troublesome to adjust optical spots into which the beams of diffracted light with the first order are focussed with respect to the information track. Further, the resulting beam of light for reading has been weakened because of loss of light.
Accordingly it is an object of the present invention to provide a new and improved system for optically reproducing a signal engraved on a record medium by using a single beam of monochromatic light with a simple optical system without the necessity of using a diffraction grating.